It is known to use chromatic confocal techniques in optical height sensors. As described in U.S. Patent Application Publication No. US2006/0109483 A1, which is hereby incorporated herein by reference in its entirety, an optical element having axial chromatic aberration, also referred to as axial or longitudinal chromatic dispersion, may be used to focus a broadband light source such that the axial distance to the focus varies with the wavelength. Thus, only one wavelength will be precisely focused on a surface, and the surface height or position relative to the focusing element determines which wavelength is best focused. Upon reflection from the surface, the light is refocused onto a small detector aperture, such as a pinhole or the end of an optical fiber. Upon reflection from a surface and passing back through the optical system to the in/out fiber, only the wavelength that is well-focused on the surface is well-focused on the fiber. All of the other wavelengths are poorly focused on the fiber, and so will not couple much power into the fiber. Therefore, for the light returned through the fiber the signal level will be greatest for the wavelength corresponding to the surface height or position of the surface. A spectrometer type detector measures the signal level for each wavelength, in order to determine the surface height.
Certain manufacturers refer to practical and compact systems that operate as described above, and that are suitable for chromatic confocal ranging in an industrial setting, as chromatic point sensors. A compact chromatically-dispersive optical assembly that is used with such systems is referred to as an “optical pen”. The optical pen is connected through the optical fiber to an electronic portion of the CPS, which transmits light through the fiber to be output from the optical pen and provides the spectrometer that detects and analyzes the returned light. In known implementations, pixel data corresponding to the wavelength-dispersed intensity profile received by the spectrometer's detector array is analyzed to determine the “dominant wavelength position coordinate” for the intensity profile, and the resulting position coordinate is used with a lookup table to determine the position of the surface. However, in practical applications, known implementations exhibit certain undesirable measurement variations. Reducing or eliminating such measurement variations would be desirable.